In order to observe a very small area of an object, a scanning electron microscope (SEM), a transmission electron microscope (TEM), etc. are used. Generally, in these pieces of apparatus, the air is evacuated from a casing in which a sample is set, to make a sample atmosphere as a vacuum state for capturing an image of the sample. However, a biochemical sample, soft material and the like may be damaged or changed in state in the vacuum. On the other hand, a demand is growing for observing such samples with an electron microscope, which leads to development of sample storage casings with which an observed sample can be observed under atmospheric pressure or in a desired type of gas, SEM apparatus and the like.
These pieces of apparatus, in principle, have a diaphragm or minute holes through which electron beams can transmit, between an electronic optical system and a sample to separate the vacuum state from an atmospheric state. These pieces of apparatus have a diaphragm between the sample and the electronic optical system in common.
For example, Patent Document 1 discloses a sample storage container having a diaphragm through which electron beams transmit on an upper surface side. Reflected electrons or secondary electrons from the sample, which have contacted the diaphragm, are detected for an observation with a SEM. The sample is maintained in a space formed by an annular member arranged around the diaphragm and the diaphragm, and the space is filled with liquid such as water.
In addition, Patent Document 2 discloses a SEM in which an electron source side of an electron optical column is arranged to face downward, an object lens side is arranged to face upward, and a diaphragm is arranged via an O-ring on an emitting hole of electron beams at an end of the electron optical column such that the electron beams can transmit. In the invention disclosed in the Patent Document 2, an observed sample is directly set on the diaphragm, and primary electron beams are irradiated from a lower surface of the sample to detect reflected electrons or secondary electrons for an observation with the SEM. The sample is maintained in a space formed by an annular member arranged around the diaphragm and the diaphragm, and the space is filled with liquid such as water.